Automatic safety trap for refrigerating machines



Aug. 3 1926. 1,594,422

A. T. MARSHALL AUTOMATIC SAFETY TRAP FOR REFRIGERATING MACHINES FiledDec. 4, 1924 l I in n Gila/rs amp/1R4? sac/r P/rsnswrf snare/v 3 a q 7r/ro/v EXPANSION 00/4 sou s r/PA P a 3 CG/VDEA/SEF? i To r lmmvslolv Wuv4 RECEIVER INVENTOR ALTIORNEYF Patented Aug. 3, l 926.'

UNITED STATES PATENT OFFICE.

ALBERT T. MARSHALL, OF JEARTFORD, CONNECTICUT, ASSIGNOR TO THE AUTOMATICREFRIGERATING COMPANY OF HARTFORD, CONNECTICUT, A CORPORATION OF 7 NEWJERSEY.

AUTO MATIC SAFETY TRAP FOB REFBIGERATING MACHINES.

Application filed December 4, .1924. Serial No. 753,961.

This invention relates to refrigerating apparatus using a condensab'levapor. In such apparatus trouble sometimes occurs from the.

passage over to, the compressor of slugs of liquid which mayresult-inthe blowing out of the. cylinder head or other damage. Ordinarily, thesmallscale trap that is interposed in 'the return line from theexpansion coils is sufiicient to intercept such slugs of liquid and holdthem until they re-evaporate I under the suction action of thecompressor,

particularly if a choke diaphragm or equivalent device is interposed inthe pipe between the trap and the compressor. At other times, the amountof'liquid coming over may be so great as to more than fill the scaletrap.

The object of the present invention isto' provide means whereby suchexcessive amounts of liquid will be automaticall removed I from thesuction conduits an returned to the liquid receiver, and in the event ofthe li uid coming over in an amount greater t an the return apparatus,can take care of, I provide means whereby,

in such event the compressor is automatically stopped and again startedwhen the liquid isdisposed of to a sufficient amount to make itsoperation safe. i

The inventioni' will be further described in connection with theaccompanying drawings, in which a Figure 1 is a; diagram of refrigeratinapparatus to which my invention is appli Figure 2 is a detail mechanism.I

Figure 3 is a detail view of a modification of part of the apparatus insection.- I

' of the top part view of the switcli Figure 4 is an outside view ofsaid modification. y

A receiver 1, containing a reservoir of condensed vapor, has a pipe 2leading to an expansion valve which feeds the expansion or refrigeratingcoils. I Areturn pipe 3 from the expansion coils leads to the suction ofa compressor 4 and a-pipe 5 takesthe compressed vapor from thecompressor to the condenser 6t A scale trap,- 7' is inter .poseclin thesuction line and. at '8 may be introduced a choke diaphragm in which thevapor is compelled to pass through an orifice very much smaller than thecross section of the pipe 3, with the result that any slugs of liqluldpassing through will be heldup and on y so much allowed to pass as thecom- 14 to, for example, the receiver 1.

pressor can take care of. A back pressure switch is shown at 9,-whichserves the usual purpose of stopping the compressor when the pressure inthe suction line falls below a certain limit, and restartingthecompressor when the said pressure-returns to a predetermined point. Whenlarger amounts of liquid come over than the scale trap can take care of,I provide means whereby the surplus liquid can be automatically drainedaway as follows i A drain pipe 10 from the scale trap discharges theliquid from the scalev trap into a safety trap 11 which is of ample sizeto take care of such excessive amounts of liquid. A pipe 12 leads fromthe bottom of the safet trap. tov a pump 13 which pumps the liqui fromthe safety trap through safety trap 11 should be surrounded with' corkor other heat insulation 15 and is'shown mounted on the latform of aweighing scale 16, the weight I cam 17 of which has the usua adjustingweights 18 held on its outer end. Mounted on a stationary support is anelectric switch 19 which may be of the usual quick-acting, snap overtype. It is operated by a rod 20 which impinges against the scale beain17, against whlch it is held either by its own weight or by weightassisted by the spring 21. Adjustable stops 22 onthe rod determineaccurately at 'what point the said stops actuate the trig 23 that, :13;means of. spring 24, acts to t row the swi 19 either up against Contact25 or down against rest 26. From contact 25 and switch 19, circuits leadto the motor driving the liquid pump 13. In addition to the adjustableweights 18 on-the scale beam, I provide an additional weight 27 heldnormally suspended on supports 28 from the frame. An adjustable piece 29on the weight rod 30 is adapted to lift the weight 27 and transfer itsweight'from supports 28 to the rod 30 when the weight of the liquidaccumulated in the safety trap exceeds a certain amount. Before thisoccurs, the scale beam V value t at control electromal. tip the scalebeam stil'l further member 29 to lift the weight on this occurs, thescale beam going up further, will lift 0 eratin rod 31 01 an additionalswitch 32. is swltch may be a quick-acting switch as is the switch 19."When the rod 31 is thus pushed up by the scale beam, the switch 32breaks the circuit of the motor driving compressor so that thecompressor will be stopped before any damage from furtheraccumulation ofliquid may occur. While I have shown these electric switches 19 and 32as being placed directly in the circuits of the motors, they are, inpractice, preferably of the relay type and onl operate circuits'of smallcurrent etic main switches in the motor circuits 1n a manner weliunderstood in the art. It is, of course, understood that pipes'lO and 12supplying iiquid to and from the safety trap, will be flexible enough topermit the free vertical motion of the trap. As the total vertical movision in the pi e tion of the trap is a small fraction of an inch, thisdoes not require any special proalthough such special provision may, 0course, be made. The safety trap just described, thus serves to trap acertain amount of liquid, which may be rep evaporated by the suction ofthe pump with-- out actuating the weighing mechanism. Should it,however, accumulate faster than the compressor can take care of it, itwill,

after arriving at a certain level, cause, by its weight, an lnitialmovement of the scale-v beam whereby the weights 18 are lifted until,the member 29 rests against the weight 27.

' cum'ulates.

started and ordinarily will safety trap.-' When the trap is sufficientlyAt this point, the liquid ump 13 will be soon empty the evacuated, theweight 18 will again descend, which will result in the opening of thecircuit of the motor driving the liquid pump, thus causing a cessationof the operation of the pump until the liquid again achould, however,the accumulatron of liquid continue .at a rate that the small pump 13 isnot able totake care of,

the added weight in the trap will cause a further movement of thescale-beam whereby .member 29 will be enabled to lift the wei ht 27 andthis will cause theo ration 1e switch 32' and shut down tli: comressor.The, compressor maysubsequently started up aga n by the operator, or, ifdesired, the compressor may be automatically restarted by the closing Yin of the circuit of its driving motor w on the evacuat1on of the tra bythe liquid pump brings the wei ht of iquid in the trap down to a point were it would be safe for the compressor to again start the suction.

In Fi re 3 I have shown another way of accomplishing the'same result.Here a stationary trap 34 has a float 35 which is supported on a spring36. This float moves f other fol owing upon further accumulation ofliquid, to stop the compressor. While I have shown two means of carryinmy invention into effect, I do not wish to limited specifically thereto,as there are alter native means that could be equally applicable. Theliquid pump could be started and stopped by mechanical means instead ofelectrical and the trapped liquid may be returned to any part of thesystem suitable to receive it. In some cases this might be part of theexpansion side, like coils or cooler in large brine tank. For causingthe weight of liquid in the trap to operate the switches, I have shownan ordinary form of platform weighin scale but the same re-v sult couldbe obtained if the trap were suspended by suitable levers that. wouldgive the desired multiplied motion. The scale trap can be. omitted andsafety trap serve the purpose of both.. The action of the ac cumulationof liquid in the trap 11 in operating the switches to start and stop themotors requires a certain amount of time.

In other words, it is necessary that the scale beam does not movequickly from one position to another but that its action be delayed inorder that the-trap may have time to fill or em ty as the case may be,so as to not have t e starting and stopping of the motors occur moreoften than necessary. This de-' layed action may, for. example, bebrought about by the tension of the springs 24 of the electric switchesacting to hold .in restraint the rod 20 until the maximum and minimumweights in the trap are reached.

In the same way, the spring 24 of the switch- 32 will restrain theoperatlon of rod 31 until the desired additional accumulation orreduction of liquidin the trap takes place. A spring 43 whose tension isadjustable by means .of an adjusting screw 44, may be used to regulatethe resistance to the movement of the scale beam under the action of theliquid in the trap. In Figure 2 I have shown in a dotted" line diagram,means whereby the movement of the scale lever acting under the combinedeffect of the changeable weight of the liquid trap, the weig ts 18 and27, and the spring 43, may act to close and open relay circuits from asource of electricity, shown at 45, whereby the compressor willordinarily take care of further accumulations but the liquid pump willcontinue to operate until contact 46 reaches terminal 47 when the trapbeing a contact arm 46 will-contact with terminals 47 and 48 near thelower and upper limits of the motion of the scale beam,to operate athrow-over switch 49 by means of electromagnets 50. and. 51, to open thecircuit of he liquid pump motor when the scale beam is near itslowermost position, and to close the same when the scale beam is nearits uppermost position. It will be noted that such a switch operatesonly when the scale beam nears lts extreme posit on and 1s mactive atintermediate points.

vations of the scale beam, make contact with terminals 52 and 53, which,operating through electromagnets 54 and 55, will control a switch 56that will operate at the proper times to close or open the circuits 33of the motor driving the compressor. It

will beunderstood that with such switches, the scale control spring 43will keep the.

scale resistance to the weight of the liquid in the" trap in. balance,which, in the ordinary operation of the plant, will mean that the liquidpump is not running and the compressor is running, the fluctuations ofliquid in the trap, if any, being not sufii driving the liquid pump andthus start the evacuation of the trap, returning the liquidv therein tothe receiver or'a-ny other suitable location. Ordinarily the operationof the liquid pump will prevent further accumulation of liquid in thetrap and decrease the same until the trap is nearly or quite empty whencontact 46 will touch terminal 47 and open the circuit ofthe liquid pumpmotor. If the operation of the pump is not suflicient to take care ofthe accumulation of liquid in the trap, the scale beam will lift thescale. beam consequent thereupon, the p st11l further and when contact46 touches terminal 53, the magnet 55 will operate switch 56 to open thecircuit 33 of the compressor motor, thus shuttin down the compressorbefore damage can done by overflow of liquid into the compressorcylinders. With the compressor thus shut down, the pump will be enabledto evacuate the trap and at some suitable point-in the descent ofcontact 46 will touch terminal 52 and restart the com ressor by theoperation of magnet 54 closing switch 56. "From there on emptied, thepump motor will be stopped. It will be seen .from the above that I haveSimilarly,

. the contact 46 may at lower and higher eler provided means wherebyabnormal accumulation of liquid in the trap will start a pump or othermeans which may, of course be a release valve to bring" about thereduction of the accumulation and that upon still further accumulationbeyond the ability of such means to take: care of, still other means areprovided for, in that event shutting down the compressor and that uponthe reduction of the weight of 1i uid in the trap to a desired minimum,t ese operations are reversed.

I claim 1. The method of preventing excessiveamounts of liquid fromentering the suction of the compressor of a refrigerating system, whichconsists in running such excessive liquid into a trap and causing theaccumulation of weight of theliquid in the trap to operate electricswitches to start a pump that will. evacuate the trap when theaccumulation of liquid in the trap exceeds a certain amount and upon thefurther 110- cumulation of liquid in the trap to stop the compressor anda ai'n start the compressor when the liquid 1n the trap is reduced apredetermined amount.

2. In a refrigerating system using a condensable vapor, the combinationcomprisinga compressor having suction and delivery pipes, a trap forliquid in the suction pipe, means operated by the weight of accumulatedliquid inthe trap to force the a liquid from the trap into the deliverypipe, and other means for stopping the compressor upon furtheraccumulation of liquid in the trap. I

3. In a refrigerating system using a condensable vapor, the combinationcomprising a compressor having suction and delivery pipes, a trap forliquid in the suction pipe, means operated by the weight of accumulatedliquid in the trap to force the li aid from the trap into the deliverypipe, other means for stopping the compressor upon further accumulationofliquid in the.

trap, and means for restarting the compressor when the weight reduces.

. 4. In a refrigerating system using a condensable vapor, thecombination comprising a compressor havingv suction and delivery pipes,atrap for liquid in the suction pipe, means operated by the weight of.ac cumulated liquid in the trap to force the li uid from the trap intothe delivery pipe, other means for stopping the compressor upon furtheraccumulation of liquid in the trap, and means for restarting thecompressor when the weight reduces and stop pingthe liquid pump uponstill further reduction 0 weight. 1 I

5. In a refrigerating system using a condensable vapor, the combinationcomprising a compressor having suction and delivery pipes, a trap forliquid in the suction pipe, means operated by the weight ofaccumulatedliquid in the trap to force the liquid fromthe trap, andmeans for opposing a cumulative resistance to the weight operated meansto.delay the action of the said weight operated means until a desiredmaximum accumulation has been reached.

6. In a refrigerating system using a con densable vapor, the combinationcomprising a compressor having suction and delivery pipes, a trap forliquid in the suction pipe,

means operated by the weight of accumulated liquid in the trap to forcethe liquid from the trap, and adjustable means for opposing a cumulativeresistance to the weight operated means to delay the action of the saidWeight operated means until a desired maximum accumulation has beenreached.

ALBERT T. MARSHALL.

